1. Field of the Invention
The present invention generally relates to a handheld device, and more particularly, to a device having a metallic frame body on which at least a ground point is disposed.
2. Description of Related Art
An antenna is one of indispensable parts for comprising a wireless communication device. In fact, the antenna is vital for the communication quality and the applicable range of a wireless communication device. Along with the popularity of wireless communication devices, it is increasingly paid attention the issue regarding the impact of the electromagnetic wave radiated from an antenna on human body. In this regard, The Federal Communications Commission (FCC) has defined the specific absorption ratio (SAR) of a wireless communication device so as to restrict the permissible radiation energy or the maximum permissible radiation limit.
Among many antenna architectures, the planar inverted F antenna (PIFA) is advantageous in small SAR, low cost, high radiation efficiency and easiness of miniaturization design, etc., so that the PIFA is broadly used in wireless communication devices. FIG. 1A is a cross-sectional diagram of a traditional PIFA. Referring to FIG. 1A, a PIFA 100 includes an antenna radiator 110, a feeding portion 111 and a ground portion 112, wherein the ground portion 112 is electrically connected to a ground plane on a printed circuit board (PCB) 120 and the feeding portion 111 is for delivering the signal received by the antenna radiator 110 to an integrated circuit (IC) on the PCB 120.
Generally, the bandwidth of the PIFA 100 is directly proportional to the height of the antenna. In other words, the larger the spacing between the PIFA 100 and the PCB 120, the wider the bandwidth thereof is. However, the larger spacing would make the antenna unable to meet the requirement of a communication device oriented by thin-shape style design. In order to improve the situation, a traditional hybrid antenna is provided. FIG. 1B is a cross-sectional diagram of a traditional hybrid antenna. Referring to FIG. 1B, a PIFA 100 is corresponding to a clearance area 130 so as to form a hybrid antenna, where the PIFA 100 corresponding to the clearance area 130 has a sufficient bandwidth to overcome the restriction of the height.
It should be noted that the most of the modern wireless communication devices have a style design with metallic sense so as to attract the attentions of the consumers. With such design idea, the most portions of the body of a wireless communication device is clad by metal (for example, metallic frame), which is unable to form a clearance area serving for the PIFA; or in a better situation, there is an overlapping portion formed between the antenna area and the metallic frame. In this regard, the most of the modern wireless communication devices are unable to adopt a hybrid antenna to overcome the restriction of the antenna height.